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Blown Control Valve Cover

As part of project commissioning activity, a number of actuated valves on a gas metering system, including a pressure control valve, were to be held open to allow hydro testing to be completed.

Description of Incident:

The pressure control valve was opened by connecting Pidgy tubing straight to the valve actuator from the platform instrument air supply. This was an unregulated air supply from the instrument air manifold direct to the valve bonnet air inlet which meant that the inline controls were bypassed.

Once the pressure control valve was fully open the air supply was locked in and the personnel left the area.

Shortly later, upon their return to the area, a loud bang was heard and it was identified that a section of the pressure control valve actuator cover plate had blown off the valve bonnet creating a projectile.

The cover plate, weighing 300g, did not make contact with any personnel involved with the task. All work was stopped and the job made safe.

Good Practice Guidance:

Sites should ensure that:

- Regulators, the correct test equipment for the task and suitably rated PRVs are used for any work scope involving pressure related activities.

- Suitable disciplines are chosen as Performing Authorities or alternatively the PA should be classed as a Supervising Performing Authority with someone else identified to provide the technical knowledge.